Method and apparatus for changing state of nan terminal in wireless communication system

ABSTRACT

An embodiment of the present invention relates to a method for changing the state of a neighbor awareness networking (NAN) terminal in a wireless communication system, the method comprising the steps of: receiving a synchronization beacon frame from less than three terminals, within a discovery window; and changing the state on the basis of anchor master information of the synchronization beacon frame, wherein a received signal strength indication (RSSI) of the synchronization beacon frame is between a first value and a second value, and if an anchor master rank value included in the synchronization beacon frame is greater than that stored in the terminal, the terminal converts the state from an asynchronous state to synchronous state.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for changing a state of aNAN (neighbor awareness networking) terminal.

BACKGROUND ART

Recently, various wireless communication technologies have beendeveloped with the advancement of information communication technology.Among the wireless communication technologies, a wireless local areanetwork (WLAN) is the technology capable of accessing the Internet bywireless in a home, a company or a specific service provided areathrough portable terminal such as a personal digital assistant (PDA), alaptop computer, a portable multimedia player (PMP), etc. based on aradio frequency technology.

DISCLOSURE OF THE INVENTION Technical Task

The technical task of the present invention is to define a statechange/transition of a NAN (neighbor awareness networking) terminal.

Technical tasks obtainable from the present invention are non-limited bythe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solutions

In a 1^(st) technical aspect of the present invention, provided hereinis a method of changing a state of a NAN (neighbor awareness networking)terminal in a wireless communication system, including the steps ofreceiving a synchronization beacon frame from less than three terminalswithin a discovery window and changing the state based on anchor masterinformation of the synchronization beacon frame, wherein when an RSSI(received signal strength indication) of the synchronization beaconframe is between a first value and a second value and when an anchormaster rank value included in the synchronization beacon frame is higherthan that stored in the terminal, the terminal changes from anon-synchronization state to a synchronization state.

In a 2^(nd) technical aspect of the present invention, provided hereinis a NAN (neighbor awareness networking) terminal in a wirelesscommunication system, including a receiving module and a processor,wherein the processor is configured to receive a synchronization beaconframe from less than three terminals within a discovery window and tochange a state based on anchor master information of the synchronizationbeacon frame and wherein when an RSSI (received signal strengthindication) of the synchronization beacon frame is between a first valueand a second value and when an anchor master rank value included in thesynchronization beacon frame is higher than that stored in the terminal,the terminal changes from a non-synchronization state to asynchronization state.

The following matters may be included in the 1^(st) and 2^(nd) technicalaspects of the present invention.

When the RSSI of the synchronization beacon frame is between the firstvalue and the second value and when the anchor master rank valueincluded in the synchronization beacon frame is equal to that stored inthe terminal, the terminal may change to the synchronization state onlyif a hop count value of each of the less than three terminals is lowerthan a hop count value of the terminal.

When the RSSI of the synchronization beacon frame is between the firstvalue and the second value and when the anchor master rank value and ahop count value included in the synchronization beacon frame are equalto those stored in the terminal respectively, the terminal may change tothe synchronization state only if a master rank value of each of theless than three terminals is higher than a master rank value of theterminal.

The first value and the second value may correspond to an RSSI_middleand an RSSI_close, respectively.

The first value may be greater than −60 dBm and the second value may begreater than −75 dBm and less than the first value.

The anchor master information may include an anchor master rank, a hopcount, and an anchor master beacon transmission time.

The state change may be performed at an end of the discovery window.

When the terminal enters a cluster in a Sync state, the terminal mayomit synchronization beacon frame transmission in a first discoverywindow.

When the terminal enters a cluster in a Sync sate, the terminal maytransmit a synchronization beacon frame after setting a back-off countvalue based on a synchronization beacon frame received in a firstdiscovery window.

When the terminal enters a cluster from intervals except the discoverywindow in a Sync state, the terminal may transmit a synchronizationbeacon frame after setting a back-off count value based on a hop countvalue included in a discovery beacon frame.

When the terminal enters a cluster in a Sync state, the terminal mayperform anchor master selection in a first discovery window and transmita synchronization beacon frame from a second discovery window.

The terminal can enter a cluster only in a Non-Master Non-Sync state.

Advantageous Effects

According to the present invention, a NAN terminal can perform a statechange/transition correctly.

Effects obtainable from the present invention are non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a diagram illustrating an exemplary structure of IEEE 802.11system.

FIGS. 2 and 3 are diagrams illustrating examples of a NAN cluster.

FIG. 4 illustrates an example of a structure of a NAN device (terminal).

FIGS. 5 and 6 illustrate relations between NAN components.

FIG. 7 is a diagram illustrating a state transition of a NAN device(terminal).

FIG. 8 is a diagram illustrating a discovery window and the like.

FIG. 9 is a diagram for describing anchor master selection.

FIG. 10 is a block diagram illustrating a configuration of a wirelessdevice according to one embodiment of the present invention.

BEST MODE FOR INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The detailed description, which will be given below withreference to the accompanying drawings, is intended to explain exemplaryembodiments of the present invention, rather than to show the onlyembodiments that can be implemented according to the present invention.The following detailed description includes specific details in order toprovide the full understanding of the present invention. However, itwill be apparent to those skilled in the art that the present inventionmay be implemented without such specific details.

The following embodiments can be achieved by combinations of structuralelements and features of the present invention in prescribed forms. Eachof the structural elements or features should be considered selectivelyunless specified separately. Each of the structural elements or featuresmay be carried out without being combined with other structural elementsor features. Also, some structural elements and/or features may becombined with one another to constitute the embodiments of the presentinvention. The order of operations described in the embodiments of thepresent invention may be changed. Some structural elements or featuresof one embodiment may be included in another embodiment, or may bereplaced with corresponding structural elements or features of anotherembodiment.

Specific terminologies in the following description are provided to helpthe understanding of the present invention. And, these specificterminologies may be changed to other formats within the technical scopeor spirit of the present invention.

Occasionally, to avoid obscuring the concept of the present invention,structures and/or devices known to the public may be skipped orrepresented as block diagrams centering on the core functions of thestructures and/or devices. In addition, the same reference numbers willbe used throughout the drawings to refer to the same or like parts inthis specification.

The embodiments of the present invention can be supported by thedisclosed standard documents disclosed for at least one of wirelessaccess systems including IEEE 802 system, 3GPP system, 3GPP LTE system,LTE-A (LTE-Advanced) system and 3GPP2 system. In particular, the stepsor parts, which are not explained to clearly reveal the technical ideaof the present invention, in the embodiments of the present inventionmay be supported by the above documents. Moreover, all terminologiesdisclosed in this document can be supported by the above standarddocuments.

The following embodiments of the present invention can be applied to avariety of wireless access technologies, for example, CDMA (codedivision multiple access), FDMA (frequency division multiple access),TDMA (time division multiple access), OFDMA (orthogonal frequencydivision multiple access), SC-FDMA (single carrier frequency divisionmultiple access) and the like. CDMA can be implemented with such a radiotechnology as UTRA (universal terrestrial radio access), CDMA 2000 andthe like. TDMA can be implemented with such a radio technology asGSM/GPRS/EDGE (Global System for Mobile communications)/General PacketRadio Service/Enhanced Data Rates for GSM Evolution). OFDMA can beimplemented with such a radio technology as IEEE 802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE 802.20, E-UTRA (Evolved UTRA), etc. For clarity,the following description focuses on IEEE 802.11 systems. However,technical features of the present invention are not limited thereto.

Structure of WLAN System

FIG. 1 is a diagram illustrating an exemplary structure of IEEE 802.11system to which the present invention is applicable.

IEEE 802.11 structure may include a plurality of components and WLANsupportive of transparent STA mobility for an upper layer can beprovided by interactions between the components. A basic service set(BSS) may correspond to a basic component block in IEEE 802.11 WLAN.FIG. 1 shows one example that two basic service sets BSS 1 and BSS 2exist and that 2 STAs are included as members of each BSS. Inparticular, STA 1 and STA 2 are included in the BSS 1 and STA 3 and STA4 are included in the BSS 2. In FIG. 1, an oval indicating the BSS canbe understood as indicating a coverage area in which the STAs includedin the corresponding BSS maintain communication. This area may be calleda basic service area (BSA). Once the STA moves out of the BSA, it isunable to directly communicate with other STAs within the correspondingBSA.

A most basic type of BSS in IEEE 802.11 WLAN is an independent BSS(IBSS). For instance, IBSS can have a minimum configuration including 2STAs only. Moreover, the BSS (e.g., BSS 1 or BSS 2) shown in FIG. 1,which has the simplest configuration and in which other components areomitted, may correspond to a representative example of the IBSS. Such aconfiguration is possible if STAs can directly communicate with eachother. Moreover, the above-mentioned WLAN is not configured according toa devised plan but can be configured under the necessity of WLAN. And,this may be called an ad-hoc network.

If an STA is turned on/off or enters/escapes from a BSS area, membershipof the STA in a BSS can be dynamically changed. In order to obtain themembership of the BSS, the STA can join the BSS using a synchronizationprocedure. In order to access all services of the BSS based structure,the STA should be associated with the BSS. This association may bedynamically configured or may include a use of a DSS (distributionsystem service).

Additionally, FIG. 1 shows components such as a DS (distributionsystem), a DSM (distribution system medium), an AP (access point) andthe like.

In WLAN, a direct station-to-station distance can be restricted by PHYcapability. In some cases, the restriction of the distance may besufficient enough. However, in some cases, communication betweenstations located far away from each other may be necessary. In order tosupport extended coverage, the DS (distribution system) may beconfigured.

The DS means a structure in which BSSs are interconnected with eachother. Specifically, the BSS may exist as an extended type of componentof a network consisting of a plurality of BSSs instead of anindependently existing entity as shown in FIG. 1.

The DS corresponds to a logical concept and can be specified by acharacteristic of the DSM. Regarding this, IEEE 802.11 standardlogically distinguishes a wireless medium (WM) from the DSM. Each of thelogical media is used for a different purpose and is used as a differentcomponent. According to the definition of the IEEE 802.11 standard, themedia are not limited to be identical to each other or to be differentfrom each other. Since a plurality of the media are logically differentfrom each other, flexibility of IEEE 802.11 WLAN structure (a DSstructure or a different network structure) can be explained. Inparticular, the IEEE 802.11 WLAN structure can be implemented in variousways and the WLAN structure can be independently specified by a physicalcharacteristic of each implementation case.

The DS can support a mobile device in a manner of providing seamlessintegration of a plurality of BSSs and logical services necessary forhandling an address to a destination.

The AP enables associated STAs to access the DS through the WM andcorresponds to an entity having STA functionality. Data can betransferred between the BSS and the DS through the AP. For instance, asshown in FIG. 1, while each of the STA 2 and STA 3 have STAfunctionality, the STA 2 and STA 3 provide functions of enablingassociated STAs (STA 1 and STA 4) to access the DS. And, since all APsbasically correspond to an STA, all APs correspond to an addressableentity. An address used by the AP for communication in the WM should notbe identical to an address used by the AP for communication in the DSM.

Data transmitted from one of STAs associated with an AP to an STAaddress of the AP is always received in an uncontrolled port and thedata can be processed by an IEEE 802.1X port access entity. Moreover, ifa controlled port is authenticated, transmission data (or frame) can bedelivered to a DS.

Layer Structure

Operations of the STA which operates in a wireless LAN system can beexplained in terms of the layer structure. In terms of a deviceconfiguration, the layer structure can be implemented by a processor.The STA may have a structure of a plurality of layers. For example, amain layer structure handled in the 802.11 standard document includes aMAC sublayer and a physical (PHY) layer on a data link layer (DLL). ThePHY layer may include a physical layer convergence procedure (PLCP)entity, a physical medium dependent (PMD) entity, etc. The MAC sublayerand the PHY layer conceptually include management entities called MACsublayer management entity (MLME) and physical layer management entity(PLME), respectively. These entities provide a layer management serviceinterface for performing a layer management function.

A station management entity (SME) is present within each STA in order toprovide an accurate MAC operation. The SME is a layer-independent entitythat may be considered as existing in a separate management plane or asbeing off to the side. Detailed functions of the SME are not specifiedin this document but it may be generally considered as being responsiblefor functions of gathering layer-dependent status from the various layermanagement entities (LMEs), setting values of layer-specific parameterssimilar to each other. The SME may perform such functions on behalf ofgeneral system management entities and may implement a standardmanagement protocol.

The aforementioned entities interact with each other in various ways.For example, the entities may interact with each other by exchangingGET/SET primitives. The primitive means a set of elements or parametersrelated to a specific purpose. XX-GET.request primitive is used forrequesting a value of a given MIB attribute (management informationbased attribute). XX-GET.confirm primitive is used for returning anappropriate MIB attribute value if a status is ‘success’, otherwise itis used for returning an error indication in a status field.XX-SET.request primitive is used to request that an indicated MIBattribute be set to a given value. If this MIB attribute implies aspecific action, this requests that the action be performed. And,XX-SET.confirm primitive is used such that, if the status is ‘success’,this confirms that the indicated MIB attribute has been set to therequested value, otherwise it is used to return an error condition inthe status field. If this MIB attribute implies a specific action, thisconfirms that the action has been performed.

Moreover, the MLME and the SME may exchange various MLME_GET/SETprimitives through an MLME SAP (service access point). Furthermore,various PLME_GET/SET primitives may be exchanged between the PLME andthe SME through PLME_SAP and may be exchanged between the MLME and thePLME through an MLME-PLME_SAP.

NAN (Neighbor Awareness Network) Topology

A NAN network can be constructed with NAN devices (terminals) that use aset of identical NAN parameters (e.g., a time interval betweenconsecutive discovery windows, an interval of a discovery window, abeacon interval, a NAN channel, etc.). A NAN cluster can be formed byNAN terminals and the NAN cluster means a set of NAN terminals that aresynchronized on the same discovery window schedule. And, a set of thesame NAN parameters is used in the NAN cluster. FIG. 2 illustrates anexample of the NAN cluster. A NAN terminal included in the NAN clustermay directly transmit a multicast/unicast service discovery frame to adifferent NAN terminal within a range of the discovery window. As shownin FIG. 3, at least one NAN master may exist in a NAN cluster and theNAN master may be changed. Moreover, the NAN master may transmit all ofa synchronization beacon frame, discovery beacon frame and servicediscovery frame.

NAN Device Architecture

FIG. 4 illustrates an example of a structure of a NAN device (terminal).Referring to FIG. 4, the NAN terminal is based on a physical layer in802.11 and its main components correspond to a NAN discovery engine, aNAN MAC (medium access control), and NAN APIs connected to respectiveapplications (e.g., Application 1, Application 2, . . . , ApplicationN).

FIGS. 5 and 6 illustrate relations between NAN components. Servicerequests and responses are processed through the NAN discovery engine,and the NAN beacon frames and the service discovery frames are processedby the NAN MAC. The NAN discovery engine may provide functions ofsubscribing, publishing, and following-up. The publish/subscribefunctions are operated by services/applications through a serviceinterface. If the publish/subscribe commands are executed, instances forthe publish/subscribe functions are generated. Each of the instances isdriven independently and a plurality of instances can be drivensimultaneously in accordance with the implementation. The follow-upfunction corresponds to means for the services/applications thattransceive specific service information.

Role and State of NAN Device

As mentioned in the foregoing description, a NAN device (terminal) canserve as a NAN master and the NAN master can be changed. In other words,roles and states of the NAN terminal can be shifted in various ways andrelated examples are illustrated in FIG. 7. The roles and states, whichthe NAN terminal can have, may include a master (hereinafter, the mastermeans a state of master role and sync), a Non-master sync, and aNon-master Non-sync. Transmission availability of the discovery beaconframe and/or the synchronization beacon frame can be determinedaccording to each of the roles and states and it may be set asillustrated in Table 1.

TABLE 1 Role and State Discovery Beacon Synchronization Beacon MasterTransmission Possible Transmission Possible Non-Master Sync TransmissionImpossible Transmission Possible Non-Master Transmission ImpossibleTransmission Impossible Non-Sync

The state of the NAN terminal can be determined according to a masterrank (MR). The master rank indicates the preference of the NAN terminalto serve as the NAN master. In particular, a high master rank meansstrong preference for the NAN master. The NAN MR can be determined byMaster Preference, Random Factor, Device MAC address, and the likeaccording to Formula 1.

MasterRank=MasterPreference*2⁵⁶+RandomFactor*2⁴⁸−MAC[5]*2⁴⁰+. . .+MAC[0]  [Formula 1]

In Formula 1, the Master Preference, Random Factor, Device MAC addressmay be indicated through a master indication attribute. The masterindication attributes may be set as illustrated in Table 2.

TABLE 2 Field Name Size (Octets) Value Description Attribute ID 1 0x00Identifies the type of NAN attribute. Length 2 2 Length of the followingfield in the attribute Master Preference 1 0-255 Information that isused to indicate a NAN Device's preference to serve as the role ofMaster, with a larger value indicating a higher preference. RandomFactor 1 0-255 A random number selected by the sending NAN Device.

Regarding the above MR, in case of a NAN terminal that activates a NANservice and initiates a NAN cluster, each of the Master Preference andthe Random Factor is set to 0 and NANWarmUp is reset. The NAN terminalshould set a Master Preference field value in the master indicationattribute to a value greater than 0 and a Random Factor value in themaster indication attribute to a new value until when the NANWarmUpexpires. When a NAN terminal joins a NAN cluster in which the MasterPreference of an anchor master is set to a value greater than 0, thecorresponding NAN terminal may set the Master Preference to a valuegreater than 0 and the Random Factor to a new value irrespective ofexpiration of the NANWarmUp.

Moreover, a NAN terminal can become an anchor master of a NAN clusterdepending on an MR value. That is, all NAN terminals have capabilitiesof operating as the anchor master. The anchor master means the devicethat has a highest MR and a smallest AMBTT (anchor master beacontransmit time) value and has a hop count (HC) (to the anchor master) setto 0 in the NAN cluster. In the NAN cluster, two anchor masters mayexist temporarily but a single anchor master is a principle of the NANcluster. If a NAN terminal becomes an anchor master of a currentlyexisting NAN cluster, the NAN terminal adopts TSF used in the currentlyexisting NAN cluster without any change.

The NAN terminal can become the anchor master in the following cases: ifa new NAN cluster is initiated; if the master rank is changed (e.g., ifan MR value of a different NAN terminal is changed or if an MR value ofthe anchor master is changed); or if a beacon frame of the currentanchor master is not received any more. In addition, if the MR value ofthe different NAN terminal is changed or if the MR value of the anchormaster is changed, the NAN terminal may lose the status of the anchormaster. The anchor master can be determined according to an anchormaster selection algorithm in the following description. In particular,the anchor master selection algorithm is the algorithm for determiningwhich NAN terminal becomes the anchor master of the NAN cluster. And,when each NAN terminal joins the NAN cluster, the anchor masterselection algorithm is driven.

If a NAN terminal initiates a new NAN cluster, the NAN terminal becomesthe anchor master of the new NAN cluster. If a NAN synchronizationbeacon frame has a hop count in excess of a threshold, the NANsynchronization beacon frame is not used by NAN terminals. And, otherNAN synchronization beacon frames except the above-mentioned NANsynchronization beacon frame are used to determine the anchor master ofthe new NAN cluster.

If receiving the NAN synchronization beacon frame having the hop countequal to or less than the threshold, the NAN terminal compares an anchormaster rank value in the beacon frame with a stored anchor master rankvalue. If the stored anchor master rank value is greater than the anchormaster value in the beacon frame, the NAN terminal discards the anchormaster value in the beacon frame. If the stored anchor master value isless than the anchor master value in the beacon frame, the NAN terminalnewly stores values greater by 1 than the anchor master rank and the hopcount included in the beacon frame and an AMBTT value in the beaconframe. If the stored anchor master rank value is equal to the anchormaster value in the beacon frame, the NAN terminal compares hopcounters. Then, if a hop count value in the beacon frame is greater thana stored value, the NAN terminal discards the received beacon frame. Ifthe hop count value in the beacon frame is equal to (the stored value—1)and if an AMBTT value is greater than the stored value, the NAN terminalnewly stores the AMBTT value in the beacon frame. If the hop count valuein the beacon frame is less than (the stored value—1), the NAN terminalincreases the hop count value in the beacon frame by 1. The stored AMBTTvalue is updated according to the following rules. If the receivedbeacon frame is transmitted by the anchor master, the AMBTT value is setto the lowest four octets of time stamp included in the received beaconframe. If the received beacon frame is transmitted from a NAN master ornon-master sync device, the AMBTT value is set to a value included in aNAN cluster attribute in the received beacon frame.

Meanwhile, a TSF timer of a NAN terminal exceeds the stored AMBTT valueby more than 16*512 TUs (e.g., 16 DW periods), the NAN terminal mayassume itself as an anchor master and then update an anchor masterrecord. In addition, if any of MR related components (e.g., MasterPreference, Random Factor, MAC Address, etc.) is changed, a NAN terminalnot corresponding to the anchor master compares the changed MR with astored value. If the changed MR of the NAN terminal is greater than thestored value, the corresponding NAN terminal may assume itself as theanchor master and then update the anchor master record.

Moreover, a NAN terminal may set anchor master fields of the clusterattributes in the NAN synchronization and discovery beacon frames tovalues in the anchor master record, except that the anchor master setsthe AMBTT value to a TSF value of corresponding beacon transmission. TheNAN terminal, which transmits the NAN synchronization beacon frame orthe discovery beacon frame, may be confirmed that the TSF in the beaconframe is derived from the same anchor master included in the clusterattribute.

Moreover, a NAN terminal may adopt a TSF timer value in a NAN beaconreceived with the same cluster ID in the following case: i) if the NANbeacon indicates an anchor master rank higher than a value in an anchormaster record of the NAN terminal; or ii) if the NAN beacon indicates ananchor master rank equal to the value in the anchor master record of theNAN terminal and if a hop count value and an AMBTT value in the NANbeacon frame are larger values in the anchor master record.

NAN Synchronization

NAN terminals(devices) participating in the same NAN Cluster may besynchronized with respect to a common clock. A TSF in the NAN clustercan be implemented through a distributed algorithm that should beperformed by all the NAN terminals. Each of the NAN terminalsparticipating in the NAN cluster may transmit NAN synchronization beaconframe (NAN sync beacon frame) according to the above-describedalgorithm. The NAN device may synchronize its clock during a discoverywindow (DW). A length of the DW corresponds to 16 TUs. During the DW,one or more NAN terminals may transmit synchronization beacon frames inorder to help all NAN terminals in the NAN cluster synchronize their ownclocks.

NAN beacon transmission is distributed. A NAN beacon frame istransmitted during a DW period existing at every 512 TU. All NANterminals can participate in generation and transmission of the NANbeacon according to their roles and states. Each of the NAN terminalsshould maintain its own TSF timer used for NAN beacon period timing. ANAN synchronization beacon interval can be established by the NANterminal that generates the NAN cluster. A series of TBTTs are definedso that the DW periods in which synchronization beacon frames can betransmitted are assigned exactly 512 TUs apart. Time zero is defined asa first TBTT and the discovery window starts at each TBTT.

Each NAN terminal serving as a NAN master transmits a NAN discoverybeacon frame from out of a NAN discovery window. On average, the NANterminal serving as the NAN master transmits the NAN discovery beaconframe every 100 TUs. A time interval between consecutive NAN discoverybeacon frames is smaller than 200 TUs. If a scheduled transmission timeoverlaps with a NAN discovery window of the NAN cluster in which thecorresponding NAN terminal participates, the NAN terminal serving as theNAN master is able to omit transmission of the NAN discovery beaconframe. In order to minimize power required to transmit the NAN discoverybeacon frame, the NAN terminal serving as the NAN master may use AC_VO(WMM Access Category—Voice) contention setting. FIG. 8 illustratesrelations between a discovery window and a NAN discovery beacon frameand transmission of NAN synchronization/discovery beacon frames.Particularly, FIG. 8(a) shows transmission of NAN discovery andsynchronization beacon frames of a NAN terminal operating in 2.4 GHzband. FIG. 8(b) shows transmission of NAN discovery and synchronizationbeacon frames of a NAN terminal operating in 2.4 GHz and 5 GHz bands.

In the following description, explained are state changes/transitions ofa NAN terminal and methods for a NAN terminal to create/enter a clusteraccording to the embodiments of the present invention.

State Change/Transition of NAN Terminal

As briefly described above with reference to FIG. 7, a NAN terminal mayhave states of Master, Non-Master Sync, Non-Master Non-Sync and thelike. The transition from the Non-Master Sync state to the Non-MasterNon-Sync state can be performed according to the following descriptiononly.

When a NAN terminal changes its state based on anchor master informationin synchronization beacon frame(s) after receiving the synchronizationbeacon frame from less than three terminals within a discovery window,if RSSI (received signal strength indication) of the synchronizationbeacon frame is between a first value and a second value and if ananchor master rank value contained in the synchronization beacon frameis higher than that stored in the NAN terminal, the NAN terminal canchanges its state from Non-Sync to Sync. In this case, if the RSSI ofthe synchronization beacon frame is between the first value and thesecond value and if the anchor master rank value contained in thesynchronization beacon frame is equal to that stored in the NANterminal, the NAN terminal can change to the Sync state only when a hopcount value of each of the less than three terminals is lower than thatof the NAN terminal. Here, the first and second values correspond toRSSI_middle and RSSI_close, respectively. The first value may be greaterthan −60 dBm and the second value may be greater than −75 dBm and lessthan the first value.

The aforementioned transition from the Non-Master Sync state to theNon-Master Non-Sync state can be performed in the following cases.

At the end of a DW (discovery window), a NAN terminal in a Non-Masterrole should change its state from Non-Sync to Sync if all of thefollowing conditions are met.

First of all, the NAN terminal does not receive a synchronization beaconframe with the RSSI higher than RSSI_close (>−60 dBm, the second value)from a NAN terminal in the same NAN cluster, an anchor master rank fieldvalue of the synchronization beacon frame is equal to a value stored inthe NAN terminal, and a hop count field value of the terminal thattransmits the synchronization beacon frame is lower than a hop countvalue of the NAN terminal. Alternatively, the NAN terminal does notreceive a synchronization beacon frame with the RSSI higher than RSSIclose (>−60 dBm, the second value) from a NAN terminal in the same NANcluster, an anchor master rank field value of the synchronization beaconframe is equal to the value stored in the NAN terminal, hop count fieldvalues are equal to each other, and a master rank value of the terminalthat transmits the synchronization beacon frame is higher than a masterrank of the NAN terminal.

Secondly, the NAN terminal does not receive a synchronization beaconframe with the RSSI higher than RSSI close (>−60 dBm) (the second value)from a NAN terminal in the same NAN cluster and an anchor master rankfield value of the synchronization beacon frame is higher than the valuestored in the NAN terminal. Alternatively, the NAN terminal does notreceive a synchronization beacon frame with the RSSI higher thanRSSI_close (>−60 dBm) (the second value) from a NAN terminal in the sameNAN cluster and a master rank of the terminal that transmits thesynchronization beacon is higher than that of the NAN terminal.

Thirdly, the NAN terminal receives synchronization beacon frame(s) withthe RSSI higher than RSSI_middle (>−75 dBm, the first value) from lessthan three NAN terminals within the NAN cluster, an anchor master rankof the synchronization beacon frame is equal to that stored in the NANterminal, and a hop count field value of the terminal that transmits thesynchronization beacon frame is lower than the hop count value of theNAN terminal. Alternatively, the NAN terminal receives synchronizationbeacon frame(s) with the RSSI higher than RSSI_middle (>−75 dBm, thefirst value) from less than three NAN terminals within the NAN cluster,an anchor master rank of the synchronization beacon frame is equal tothat stored in the NAN terminal, hop count field value are equal to eachother, and a master rank value of the terminal that transmits thesynchronization beacon is higher than the master rank of the NANterminal

Finally, the NAN terminal receives synchronization beacon frame(s) withthe RSSI higher than RSSI_middle (>−75 dBm, the first value) from lessthan three NAN terminals within the NAN cluster and an anchor masterrank field value of the synchronization beacon frame is higher than thevalue stored in the NAN terminal. Alternatively, the NAN terminalreceives synchronization beacon frame(s) with the RSSI higher thanRSSI_middle (>−75 dBm, the first value) from less than three NANterminals within the NAN cluster and a master rank of the terminal thattransmits the synchronization beacon frame is higher than that of theNAN terminal.

Next, the transition from the Non-Master Sync state to the Non-MasterNon-Sync state may occur if one of the following four conditions is met.

First of all, a NAN device (terminal) receives a synchronization beaconframe with the RSSI higher than RSSI_close from a NAN device (terminal)within the same NAN cluster, an anchor master rank value of thesynchronization beacon frame is equal to that stored in the NAN device,and a hop count value of the device that transmits the synchronizationbeacon is lower than that of the NAN device. Alternatively, the NANdevice (terminal) receives a synchronization beacon frame with the RSSIhigher than RSSI_close from a NAN device (terminal) within the same NANcluster, an anchor master rank value of the synchronization beacon frameis equal to that stored in the NAN device, hop counts are equal to eachother, and a master rank value of the device that transmits thesynchronization beacon is higher than a master rank of the NAN device.

Secondly, the NAN device receives synchronization beacon frames each ofhaving the RSSI higher than RSSI_middle from three or more NAN deviceswithin the same NAN cluster, an anchor master rank value of thesynchronization beacon frame is equal to that stored in the NAN device,and a hop count value of each device that transmits the synchronizationbeacon frame is lower than that of the NAN device. Alternatively, theNAN device receives synchronization beacon frames each of having theRSSI higher than RSSI_middle from three or more NAN devices within thesame NAN cluster, an anchor master rank value of the synchronizationbeacon frame is equal to that stored in the NAN device, hop counts areequal to each other, and a master rank value of each device thattransmits the synchronization beacon is higher than that of the NANdevice.

Thirdly, the NAN device receives a synchronization beacon frame with theRSSI higher than RSSI_close from a NAN terminal within the same NANcluster and an anchor master rank value of the synchronization beaconframe is higher than that stored in the NAN device. Alternatively, theNAN device receives a synchronization beacon frame with the RSSI higherthan RSSI close from a NAN terminal within the same NAN cluster and amaster rank value of the synchronization beacon frame is higher thanthat of the NAN device.

Finally, the NAN device receives synchronization beacon frames each ofhaving the RSSI higher than RSSI_middle from three or more NAN deviceswithin the same NAN cluster and an anchor master rank value of thesynchronization beacon frame is higher than that stored in the NANdevice. Alternatively, the NAN device receives a synchronization beaconframe with the RSSI higher than RSSI_close from a NAN terminal withinthe same NAN cluster and a master rank value of the synchronizationbeacon frame is higher than that of the NAN device.

Methods for NAN Terminal to Create/Enter Cluster

When a NAN device intends to start a cluster or to join a previouslycreated cluster, the NAN device initially set its role and state toMaster and Sync. If a NAN device is in the Sync state (e.g., Master orNon-Master Sync state), the NAN device transmits a synchronizationbeacon frame through transmission and reception of synchronizationbeacon frames. To this end, a back-off count is required and the valueof the back-off count is determined based on a HC (Hop Count) value tothe anchor master in a random manner. However, when a NAN device joinsthe cluster as a master, the NAN device is unable to transmit thesynchronization beacon frame since there is no hop count value in afirst discovery window (where transmission of the synchronization beaconframe is expected (or should be performed). Thus, one of the followingmethods may be adopted in order for the NAN device to operate correctly.

During the first discovery window interval, the NAN Device does nottransmit the synchronization beacon frame but can perform anchor masterselection and a master/anchor master selection procedure.

Alternatively, during the first discovery window interval, the NANdevice receives one or more synchronization beacon frames and sets aback-off count value based on the received synchronization beaconframes. Thereafter, the NAN device can transmit its own synchronizationbeacon frame.

Alternatively, if starting a related procedure before the firstdiscovery window interval, the NAN receives one or more discovery beaconframes, obtains a hop count value from information of a clusterattribute in the received discovery beacon frames, sets a back-off countvalue based on a value of (hop count+1) (or the hop count value), andthen transmits the synchronization beacon frame in the discovery windowinterval. When joining the existing NAN cluster, the NAN device cantransmit the synchronization beacon frame within the discovery windowafter updating current anchor master information (e.g., anchor masterrank, hop count to anchor master, anchor master beacon transmission time(AMBTT)) based on the information of the cluster attribute obtained fromthe discovery beacon frames.

Alternatively, during the first discovery window interval, the NANdevice performs anchor master selection and then updates a currentanchor master record. The NAN device can transmit the synchronizationbeacon frame in a next discovery window.

Alternatively, when joining the existing NAN cluster, the NAN devicestarts in the Non-Master Non-Sync state instead of the Sync state.During the discovery window, the NAN device does not transmit thesynchronization beacon frame but the NAN device can performmaster/anchor master selection and transmit a service discovery frame.

Alternatively, when receiving the synchronization beacon frame only andjoining the existing cluster, the NAN device updates its current anchormaster record during one or more discovery window intervals. In doingso, the NAN device can transmit the synchronization beacon frame in anext discovery window.

Alternatively, after setting anchor master information to defaultvalues, the NAN device can enter the discovery window in the Masterstate.

Alternatively, before joining the existing cluster, the NAN device hasWarmUpTime (i.e., prescribed time interval). In particular, the NANdevice can update anchor master information during this time interval.

Meanwhile, if a terminal receives a synchronization beacon during a DWinterval, the terminal performs anchor master selection and thenperforms master selection and state transition. In a series of theprocesses, if anchor master information stored in the terminal needs tobe updated during the anchor master selection, the update is set to belaunched before the master selection and state transition. However, ifthe terminal operates as described above, it may cause an undesiredoperation in the course of the transition from the Non-Master Sync stateto the Non-Master Non-Sync state. Thus, during the above statetransition, the terminal is configured to operate by comparing storedanchor master information with anchor master information obtained fromthe synchronization beacon. However, if the stored anchor masterinformation is updated during the anchor master selection, it may causea problem to the above-mentioned operation.

Therefore, in case of a NAN terminal, if receiving one synchronizationbeacon, the NAN terminal performs update after completing the masterselection and state transition. This may be interpreted as that if a NANterminal needs to perform update during the anchor master selection, theNAN terminal first stores corresponding elements in temporary space andthen perform the update after completing the master selection and statetransition.

On the other hand, in case that a stored anchor master rank and hopcount are equal to an anchor master rank and hop count included in asynchronization beacon frame, related processing is not clearly definedin the conventional anchor master selection. Regarding this issue,referring to FIG. 9, when a discovery window is changed from discoverywindow 1 (i.e., DW1 in FIG. 9 (a)) to discovery window 2 (i.e., DW2 inFIG. 9 (b1) or FIG. 9 (b2)), a master rank of NAN terminal 2 next to ananchor master is changed, whereby the NAN terminal 2 updates storedanchor master information (e.g., anchor master rank, hop count, AMBTT,etc.) with its own values and then assumes itself as the anchor master.In this case, a NAN terminal that becomes the anchor master may set anAMBTT value not only to 0×00000000 as shown in FIG. 9 (b2) but also to avalue of a current TSF Timer as shown in FIG. 9 (b1).

Moreover, if the stored anchor master rank value is equal to an anchormaster value of a beacon frame, a NAN terminal compares hop counts. Inthis case, if a hop count value of the beacon frame is higher than thestored value, the NAN terminal may discard the hop count value of thebeacon frame.

If the stored AMR (anchor master rank) value is equal to that of thereceived synchronization beacon frame and if the stored hop count valueis equal to that of the received synchronization beacon frame,

As shown in FIG. 9 (b1), when the hop count value is 0, if a storedAMBTT value is lower than an AMBTT value of the received synchronizationbeacon frame, the AMBTT value is updated with the received AMBTT value.Alternatively, as shown in FIG. 9 (b2), when the hop count value is 0,if the stored AMBTT value is lower than the AMBTT value of the receivedsynchronization beacon frame, it is discarded. On the contrary, if thestored AMBTT value is greater than the AMBTT value of the receivedsynchronization beacon frame, the AMBTT value is updated with thereceived AMBTT value. If a NAN terminal becomes an anchor master, theNAN terminal sets the stored AMBTT value to 0×00000000 as shown in FIG.9 (b2). Thus, when the AMBTT value in the received synchronizationbeacon frame is 0×0000000, the NAN terminal updates its stored AMBTTvalue with 0×0000000.

If two adjacent NAN terminals have the same AMR, hop count value, andAMBTT in the same DW, the two NAN terminals compare time stamp values ofthe synchronization beacon frame and the perform update with a largervalue. In addition, it may be considered that the AMBTT value is set tothe value of the current TSF Timer. Alternatively, if a NAN terminalbecomes the anchor master, the NAN terminal resets the TSF Timer to0×00000000. Thereafter, the NAN terminal sets the AMBTT value to anactual value of the TSF Timer at which transmission of an actualsynchronization beacon frame is expected (or performed) after the reset.

FIG. 10 is a block diagram illustrating a configuration of a wirelessdevice according to one embodiment of the present invention.

Referring to FIG. 10, a wireless device 10 may include a processor 11, amemory 12, and a transceiver 13. The transceiver 13 can transmit/receiveradio signals and implement a physical layer according to, for example,IEEE 802 system. The processor 11 is connected to the transceiver 13electrically and can then implement the physical layer and/or a MAClayer according to the IEEE 802 system. Moreover, the processor 11 maybe configured to perform at least one operation of the application, theservice and the ASP layer according to the various embodiments of thepresent invention mentioned in the foregoing description. Alternatively,the processor 11 may be configured to perform operations related to adevice operating as an AP/STA. Moreover, a module for implementing theoperations of the wireless device according to the various embodimentsof the present invention mentioned in the foregoing description may besaved in the memory 12 and then driven by the processor 11. The memory12 may be included inside the processor 11 or be provided outside theprocessor 11. And, the memory 12 can be connected to the processor 11through known means.

The detailed configuration of the wireless device 10 in FIG. 10 may beimplemented such that each of the various embodiments of the presentinvention described above is applied independently or at least twothereof are simultaneously applied. And, redundant description shall beomitted for clarity.

The embodiments of the present invention mentioned in the foregoingdescription can be implemented using various means. For instance, theembodiments of the present invention can be implemented using hardware,firmware, software and/or any combinations thereof.

In case of the implementation by hardware, a method according to theembodiments of the present invention can be implemented by at least oneselected from the group consisting of ASICs (application specificintegrated circuits), DSPs (digital signal processors), DSPDs (digitalsignal processing devices), PLDs (programmable logic devices), FPGAs(field programmable gate arrays), processor, controller,microcontroller, microprocessor and the like.

In case of the implementation by firmware or software, a methodaccording to the embodiments of the present invention can be implementedby modules, procedures, and/or functions for performing theabove-explained functions or operations. Software code is stored in thememory unit and can be driven by the processor. The memory unit isprovided within or outside the processor to exchange data with theprocessor through the various means known to the public

As mentioned in the foregoing description, the detailed descriptions forthe preferred embodiments of the present invention are provided toenable those skilled in the art to implement and practice the invention.While the present invention has been described herein with reference tothe preferred embodiments thereof, it will be apparent to those skilledin the art that various modifications and variations can be made thereinwithout departing from the spirit and scope of the invention. Therefore,the present invention is not limited to the embodiments disclosed hereinbut intends to give a broadest scope that matches the principles and newfeatures disclosed herein.

INDUSTRIAL APPLICABILITY

Although the various embodiments of the present invention have beendescribed above mainly with reference to an IEEE 802.11 system, thepresent invention can be applied to various mobile communication systemsin the same manner.

What is claimed is:
 1. A method of changing a state of a NAN (neighborawareness networking) terminal in a wireless communication system, themethod comprising: receiving a synchronization beacon frame from lessthan three terminals within a discovery window; and changing the statebased on anchor master information of the synchronization beacon frame,wherein when an RSSI (received signal strength indication) of thesynchronization beacon frame is between a first value and a second valueand when an anchor master rank value included in the synchronizationbeacon frame is higher than that stored in the terminal, the terminalchanges from a non-synchronization state to a synchronization state. 2.The method of claim 1, wherein when the RSSI of the synchronizationbeacon frame is between the first value and the second value and whenthe anchor master rank value included in the synchronization beaconframe is equal to that stored in the terminal, the terminal changes tothe synchronization state only if a hop count value of each of the lessthan three terminals is lower than a hop count value of the terminal. 3.The method of claim 1, wherein when the RSSI of the synchronizationbeacon frame is between the first value and the second value and whenthe anchor master rank value and a hop count value included in thesynchronization beacon frame are equal to those stored in the terminalrespectively, the terminal changes to the synchronization state only ifa master rank value of each of the less than three terminals is higherthan a master rank value of the terminal.
 4. The method of claim 1,wherein the first value and the second value correspond to anRSSI_middle and an RSSI_close, respectively.
 5. The method of claim 1,wherein the first value is greater than −60 dBm and the second value isgreater than −75 dBm and less than the first value.
 6. The method ofclaim 1, wherein the anchor master information comprises an anchormaster rank, a hop count, and an anchor master beacon transmission time.7. The method of claim 1, wherein the state change is performed at anend of the discovery window.
 8. The method of claim 1, wherein when theterminal enters a cluster in a Sync state, the terminal omitssynchronization beacon frame transmission in a first discovery window.9. The method of claim 1, wherein when the terminal enters a cluster ina Sync sate, the terminal transmits a synchronization beacon frame aftersetting a back-off count value based on a synchronization beacon framereceived in a first discovery window.
 10. The method of claim 1, whereinwhen the terminal enters a cluster from intervals except the discoverywindow in a Sync state, the terminal transmits a synchronization beaconframe after setting a back-off count value based on a hop count valueincluded in a discovery beacon frame.
 11. The method of claim 1, whereinwhen the terminal enters a cluster in a Sync state, the terminalperforms anchor master selection in a first discovery window andtransmits a synchronization beacon frame from a second discovery window.12. The method of claim 1, wherein the terminal can enter a cluster onlyin a Non-Master Non-Sync state.
 13. A NAN (neighbor awarenessnetworking) terminal in a wireless communication system, comprising: areceiving module; and a processor, wherein the processor is configuredto receive a synchronization beacon frame from less than three terminalswithin a discovery window and to change a state based on anchor masterinformation of the synchronization beacon frame, and wherein when anRSSI (received signal strength indication) of the synchronization beaconframe is between a first value and a second value and when an anchormaster rank value included in the synchronization beacon frame is higherthan that stored in the terminal, the terminal changes from anon-synchronization state to a synchronization state.